In the pharmaceutical production field, there are commonly known and used packaging machines for automatic packaging of pharmaceutical tablets supplied in bulk into bottles.
Usually, a packaging machine of known type includes several working groups, among which, in particular, there are a device for orderly feeding and counting tablets, preferably performing a tablet quality check, and a device for filling the bottles, moving stepwise on a conveyor, with a predetermined number of tablets.
There are several types of packaging machines for automatic packaging pharmaceutical tablets into bottles, types which differ mainly by the techniques used for orderly feeding and counting the tablets.
A packaging machine belonging to a first type includes a feeding and counting device formed by a series of small bars arranged one beside another, crosswise with respect to the conveying direction and featuring a plurality of seats, each of which receives a single tablet.
The above small bars are carried along the conveying direction below a hopper, which contains a mass of tablets in bulk, so that each seat can receive a single tablet.
The small bars are then moved toward a discharge station, where the tablets are released into the bottles, by the effect of gravity, making fall one or more tablets from one of the small bars into each bottle suitably arranged on the conveyor below the hopper.
Thus, the number of seats of each small bar defines the maximum number of bottles, which can be filled simultaneously.
The machines of the above described type reach considerable operation speed (even 300-400 bottles filled in a minute), however they present many limits and drawbacks.
First of all, the seats of the small bars are not always correctly filled during the passage below the hopper, because the tablets of irregular shape can be arranged in an incorrect position with respect to the relative seat, or some seats can be occupied by tablet fragments or by a non entire tablet.
Therefore, it can quite easily happen that a bottle is filled in an incomplete, or incorrect way.
Moreover, if a defective or partially damaged tablet is detected, the above described machines are not able to reject a single defective table and therefore it is necessary to reject the whole bottle containing the defective tablet, which obviously results in considerable economic consequences.
Further drawbacks result from the complexity of the size change over operations in order to adapt the machine to operate with tablets and/or bottles of different sizes, since in order to work with each different type or size of tablets or capsules, it is necessary to substitute the whole group of the small bars.
Another known type includes packaging machines featuring a plurality of rotating discs arranged one beside another along their axis.
Each disc is driven into rotation independently from the others and features, along its circumference, a number of seats for receiving therein the tablets to be packaged.
A hopper containing a mass of tablets in bulk is situated directly above the plurality of discs.
During rotation, each disc withdraws single tablets, one by one, from the hopper.
The disc rotation brings each tablet to an instability point, and consequently makes it fall into a bottle situated below.
During this step, each tablet can be counted and its entireness can be checked by suitable check devices.
Although the above described packaging machines with discs are very fast and reliable at the tablets counting, they require the substitution of the whole group of discs each time the size and/or the shape of the tablets to be packaged is changed.
This makes the use of this type of machines particularly expensive if there are several sizes of the tablet to be packaged.
A known packaging machine of a further type includes a plurality of vibrating planes arranged in succession along the conveying path of the tablets to be packaged.
The tablets are continuously fed to the vibrating planes from a hopper, and then they are gradually spaced apart and conveyed toward a counting area, at the outlet of the vibrating planes.
The vibrating planes are usually equipped with longitudinal guides, arranged one beside another and containing each one a row of tablets.
Each tablet is counted at the outlet of the relative guide by photo-cell or capacitive sensors, generally during its fall into a channel conveying it toward the bottle to be filled.
The number of longitudinal guides situated one beside another defines the number of bottles which can be filled simultaneously.
The structure of this type of machine is usually simple and easy to maintain.
Also the size change over operations are rather simple.
On the other hand, their production rate is rather limited and not always the spacing of the tablets in the area of the outlet of the vibrating planes is optimal.
This results in considerable problems in tablets counting and checking of their entireness.
In a packaging machine of another known type, such e.g. the one described in the U.S. Pat. No. 5,463,839, the tablets to be packaged are carried by a hopper on an inclined plane equipped with a series of channels, arranged side by side, each of which receives single tablets, one by one.
The inclined plane moves the tablets toward a counting and packaging area.
The above channels have undulated extension, and the undulation amplitude is gradually decreasing.
Therefore, the tablets move faster and faster, coming close to the counting area and thus they are spaced apart, or singled out, so as to be counted during the descent into the bottles.
Also the structure of the last packaging machine is very simple, but it presents considerable drawbacks, first of all in the spacing apart of elongated or oblong tablets, since the oblong tablets can easily stick or take a crosswise position in the undulated channels, thus causing the channels obstruction, which results in an incorrect feeding and consequently filling of bottles.